Method of preparing carbon disulfide and hydrogen sulphide



United States Patent 3,082,069 METHOD OF PREPARING CARBON DISULFIDE ANDHYDROGEN SULPHIDE Arthur Ashton Banks, Widnes, England, assignor toImperial Chemical Industries Limited, London, England, a corporation ofGreat Britain No Drawing. Filed Nov. 2, 1959, Ser. No. 850,023

Claims priority, application Great Britain Nov. 12, 1958 8 Claims. (Cl.23-406) This invention relates to a process for the manufacture ofcarbon disulphide by the catalysed reaction of hydrocarbons with sulphurand more particularly to such a reaction wherein the hydrocarbonsconsist mainly of hydrocarbons containing at least carbon atoms.

It is known that the manufacture of carbon disulphide with formation ofby-product hydrogen sulphide can be eifected by reacting hydrocarbongases with sulphur in the vapour form at elevated temperatures in thepresence of a catalytic material. Catalysts which permit the formationof carbon disulphide include such materials as activated alumina, silicagel and compounds of metals of groups V, VI, VII and VIII of theperiodic table. In particular, various oxides or sulphides of iron,molyb denum and vanadium supported on activated alumina, silica gel orother porous carriers have been disclosed as useful in catalysing thereaction of hydrocarbons with sulphur.

Now with a hydrocarbon feed consisting of methane '30 and/or ethane theprocess is not complicated by sidereactions and at temperatures of 350C. to 750 C., particularly 500 C. to 700 C. in the case of methane,carbon disulphide may be produced in useful yields together withby-product hydrogen sulphide. However, it has always been recognized by(workers in this field that when the methane or ethane contains even aminor proportion of hydrocarbons having 3 or more carbon. atoms in themolecule, the reaction is complicated by the formation of tarry materialor polymeric sulphur-containing compounds formed by the breakdown andinteraction with sulphur of the said higher hydrocarbons. When usingsuch a starting material the activity of the catalyst declines, there isa reduced conversion to the product and there is contamination of theproduct and of the unreacted sulphur which is normally recycled. Naturalgases consisting essentially of methane and also containing a fewpercent, say a total of 5% C and C hydrocarbons have normally beenregarded as border-line cases for use in such a reaction, since eventhey cause severe loss in activity of the catalyst with all thecomplications attendant thereto. Strenuous attempts have been made withsome success to overcome these problems by refinements such asintroducing a proportion of an inert gas such as nitrogen in thehydrocarbon feed, usinga stoichiometric excess of sulphur and preheatingboth reactants While at the same time avoiding premixing of thehydrocarbon feed and sulphur vapour prior to passing them to thereaction zone.

While in the type of process above described it has also been statedthat the upper limit for the permissible content of higher hydrocarbonsin the starting material can be further extended to include methane orethane containing amounts exceeding 5% of hydrocarbons containing atleast 3 carbon atoms and even to such latter hydrocarbons themselves,the only detailed processes of which we are aware showing the reactionof hydrocarbons consisting essentially of hydrocarbons containing atleast 3 carbon atoms relate to a hydrocarbon feed consisting of 94%propane, 2.5% ethane and 3.5% C; hydrocarbons. However, these processesare complicated in that it is necessary to regenerate the catalyst atfrequent intervals to prevent build-up of side reactions reaching anobjectionable ex- 3,082,069 Patented Mar. 19, 1963 See 2 tent. Thus withthe feed gas just mentioned consisting essentially of propane it hasbeen found that evidence 01 side reaction occurs after only 15 minutesand the catalyst must be re-activated, for example, by treating withsulphur vapour also for a period of 15 minutes. Even witl ahydrocarbongas consisting essentially of methane anc' analysing 86%methane, 6% ethane, 4% propane, 2% C hydrocarbons and 2% pentane andhigher hydrocar bons there is evidence of catalyst deterioration inabou' half an hour and again regeneration is needed and thi: occupies asimilar period of time. An alternative proce dure described iscontinuously to withdraw a substantia proportion of the catalyst,regenerate it in a separate ves sel and return it to the process. Thetemperature user in these processes are in the range 454 C. to 704 C. but-ar formation is greater at the higher temperatures ever within thiscomparatively low temperature range.

The teaching is therefore in the catalysed reaction of hydrocarbon feedwith sulphur at the comparatively lov temperature of the order of 450 C.to 700 C. whereii the feed consists of or contains a predominant amounof hydrocarbons containing 3 carbon atoms and ever similarly with a feedconsisting mainly of methane ant ethane with only 8% of hydrocarbonshaving 3 or mor carbon atoms, that poor conversions can be expected amthat at the best this can only be avoided by repeat-ed regen eration ofthe catalyst with all the complications attendan thereto.

Very surprisingly We have now found that a hydrocar bon feed whichconsists mainly of hydrocarbons havin at least 5 carbon atoms in themolecule may be reacte in the vapour phase and in the presence of acatalyst a temperatures in the range 700 C. to 950 C. with ver highconversion to the required carbon disulphide produc over very prolongedperiods with comparative freedor from deterioration of the catalyst bydeposition of tarr and polymeric sulphuncontaining compounds thereon.

According to the present invent-ion therefore a proces for themanufacture of carbon'disulphide and by-produc hydrogen sulphidecomprises reacting a preheatet vaporised hydrocarbon feed which isliquid at norma atmospheric temperature, which is substantially completely vaporised at a temperature below 200 C. an which consists mainlyof hydrocarbons having at least carbon atoms in the molecule withsulphur vapour in th presence of a catalyst, without premixing ofreactants prio to a reaction vessel containing the catalyst, the catalyszone being maintained at a temperature in the rang 700 C. to 1300 C.

Very good results are obtained at a reaction tempera ture in theapproximate range 800 C. to 900 C.

The catalyst to be employed may be any one known tr catalyse theformation of carbon disulphide by reactio; between hydrocarbons andsulphur. By way of exampl only of catalysts which are capable ofcatalysing th reaction between hydrocarbons and sulphur and whicl may beemployed in the process of the present lIlVCl'lllOl may be mentioned:molybdenum oxide supported or gamma-alumina, nickel supported onalpha-alumina or 01 silica gel, chromium with molybdenum oxide supporteron gamma-alumina and vanadium oxide supported 01 corundum; one verysuitable catalyst is potassium vana date supported on silica gel orcorundum.

We prefer to use at least the stoichiometric amount 0 sulphur which isrequired to convert the carbon conten of the hydrocarbon to carbondisulphide and to convex aletely vaporized at a temperature below 200 C.and :onsists mainly of hydrocarbons having at least 5 carbon itoms inthe molecule. Indeed a very suitable hydro- :arbon is one consistingmainly of hydrocarbons having at least 6 carbon atoms in the molecule.For the hydro- :arbon feed aliphatic, alicyclic and aromatichydrocarbons nay be used. Very good results are obtained with aaydrocarbon feed containing a predominating amount of ;aturatedaliphatic hydrocarbons. One suitable source of lydrocarbons is to befound in low grade petroleum dis :illates which are unsuitable forspecialised uses as motor fuel. Two such petroleum distillates arediscribed in Examples 1 and 10 of the specification.

The process of the invention may be operated isothernally oradiabatically. The reaction between hydrocaraons and sulphur isexothermic above about 640 C. and n an adiabatic system wherein thereacting gases are at 1 temperature in the range 700 C. to 1000" C. theav- :rage feed temperature of the reactants should in prac- ;ice with anefiiciently lagged reactor be at least 700 C. if the reaction is carriedout isothermally then the reactor ahould be heated or cooled as may benecessary to maintain the desired reaction temperature. In eithe rcasethe sulphur may be superheated to rather above the required average feedtemperature and the hydrocarbon feed heated :o a lower temperature thanthe average feed temperature avoid substantial cracking of thehydrocarbon feed arior to entering the reaction zone.

However, sulphur vapour is extremely corrosive, par .icularly at hightemperatures towards many construcional materials which might be usedfor preheating the ;ulphur. It may be desirable therefore to keep thepreleating temperature for sulphur vapour as low as possible. Accordingto a further feature of the invention we have 10w found that usefulresults may be obtained by carryng out the reaction of hydrocarbons withsulphur in the presence of hydrocarbon which reacts exothermally withsulphur in the reaction zone. In practice this can suitably 3e achievedby adding hydrogen to the hydrocarbon feed. The effect is that by theexothermic reaction of hydrogen .vith sulphur the required temperaturemay be obtained .vithin the reaction zone while at the same timeavoiding ;he need for excessive preheating of the sulphur.

Very good results are obtained in the process of the present inventionwhen using a static catalyst bed, a pro- :edure which requires rathersimple apparatus and un- :omplicated techniques. However, a movingburden or fluidised catalyst bed may be employed, if desired.

It is a surprising feature of the present invention that hydrocarbonscontaining carbon atoms and more can be utilised in the catalysedreaction with sulphur at rather elevated temperature to give highconversions to carbon iisulphide without the need for frequentregeneration of the catalyst. However, the invention does not precludethe refinements known in themselves to be useful in the general reactionof hydrocarbons with sulphur such as diluting the hydrocarbon feed withan inert gas such as nitrogen, using particular catalysts, preheatingwhile avoiding premixing of the hydrocarbon and sulphur feed and using astoichiometric excess of sulphur to hydrocarbon. [ndeed such refinementsare extremely useful in the presant invention.

In the present invention there is no need to use superatmosphericpressure so that the care demanded in design and use of pressureequipment is avoided. The process is operated with very good results atsubstantially atmospheric pressure. In practice this is achieved byusing no more than the very small pressure required to force thereactants through the reaction vessel.

The gaseous reaction product leaving the catalyst zone :onsistsessentially of carbon disulphide, hydrogen sulphide, hydrocarbons andsulphur, from which the various :onstituents may be separated from oneanother. Thus he gases leaving the reaction zone may be cooledsufiiciently to condense the sulphur which is then recycled to theprocess. From the residual gases carbon disulphide is either absorbed ina suitable medium such as a light oil fraction from which it issubsequently stripped, or alternatively carbon disulphide is condensedfrom the residual gases by further refrigeration The hydrogen sulphidemay be absorbed in a suitable medium such as aliphatic amines from whichit is subsequently stripped. The hydrogen sulphide thus obtained may beconverted to sulphur in a Claus furnace, this sulphur also beingrecycled to the process. In one manner of converting the hydrogensulphide to sulphur in a Claus furnace part of the byproduct hydrogensulphide is oxidised to sulphur dioxide and the latter material is thenreacted with the residual by-product hydrogen sulphide to give sulphur;the sulphur doixide can however be derived from the burning of spentoxide and the sulphur dioxide is then reacted with by-product hydrogensulphide to give sulphur. Alternatively the hydrogen sulphide by-productmay be used as a raw material in other chemical processes such as, forexample, in the manufacture of sodium sulphide.

The following examples illustrate but do not limit the invention.

Where percentages are mentioned they are by weight unless otherwiseindicated. Percentages designated v are volume percentages. Thedesignation R.T.P. refers to standard temperature and pressure (0 C. and1 atmosphere pressure) and this indicates the volume which the amount ofgas referred to would have under these conditions.

Example 1 The hydrocarbon feed in this and the eight following exampleswas a petroleum distillate of average formula C H consisting essentiallyof saturated aliphatic hydrocarbons but also containing about 2% /v ofnon-aliphatic hydrocarbons of which 1% /v is naphthenes, 0.3% to 0.8% vis benzene, together with a trace of toluene. The material was ofspecific gravity 0.656 at 15.5/ 15.5 C. and 99% of the materialdistilled in the range 36.5 C. to 90 C. The hydrocarbon feed was'vaporised and diluted with nitrogen. This material fed at a ratecorresponding to 4 g./hr. of hydrocarbon (equivalent to 1.1 l./hr. atR.T.P.) and 11 l./hr. nitro gen (at R.T.P.) on the one hand, and sulphurvapour on the other hand at the rate of 42 g./hr. (equivalent to 14.7l./hr. at R.T.P.) were separately introduced into the catalyst whichconsisted of potassium vanadate on silica gel. The catalyst occupied avolume of 50-60 ml. and the catalyst zone was maintained at atemperature of 900 C. The space velocity was 600 hr.- A conversionefiioiency based on hydrocarbons of 92% was realised over a period of130 hours and at the end of this time there was no evidence of anydeterioration in the conversion efiiciency.

Example 2 The general procedure outlined in Example 1 was repeatedexcept that the hydrocarbon feed was not diluted with nitrogen and thespace velocity was 300 hI. A conversion etficiency of 95% was maintainedover a period of hours.

Example 3 The procedure outlined in Example 2 was repeated with theexception that the catalyst zone was maintained at a temperature of 700C. A conversion efficiency of 7580% was maintained over a period ofhours.

Example 4 The procedure outlined in Example 3 was repeated with theexception that the catalyst was a composition comprising potassiumvanadate supported on corundum (analysing 0.8% K and 4.3% V). Aconversion efliciency of 75% was maintained over a period of 40 hours.

Example 5 The process of Example 4 was repeated except that the catalystwas a composition comprising vanadium oxide supported oncorundurn, thecomposition containing sodium and potassium as an impurity only to theamount of 0.2% Na and 0.1% K. The conversion efliciency was 69% andcarbon deposition in the catalyst chamber and in the exit gases was muchgreater than that observed in Examples 3 and 4.

Example 6 In this example the catalyst consisted of 60 g. of particles0.5 cm. in their greatest dimension consisting of 20% by Weight of amolybdenum oxide supported on gamma-alumina. The previously describedhydrocarbon feed was vaporised and diluted with nitrogen. This materialat the rate of 3.92 g./hr. of hydrocarbon (equivalent to 1.1 =l./hr. atR.T.P.) with 11 l./hr. nitrogen on the one hand and sulphur vapour atthe rate of 14.7 -l./hr. (at R.T.P.) on the other hand were separatelyintroduced into the reaction zone which was maintained at a temperatureof 800 C. The space velocity was 535 hrr After a period of 43 hours aconversion efficiency of 91% based on the hydrocarbon feed was stillbeing obtained.

Example 7 The general procedure of Example 6 was repeated but in (thiscase the catalyst composition weighed 50 g. and comprised 8% by weightof nickel supported on alphaalumina, the particle size of the catalystbeing in this case 0.3 cm. to 0.5 cm. A conversion efliciency to carbondisulphide based on the hydrocarbon feed of 86% was still beingmaintained after 35 hours.

Example 8 The general procedure of Example 7 was repeated but in casethe catalyst composition weighed 20 g. and comprised 8% by weight ofnickel supported on silica.

A conversion efficiency to CS based on the hydrocarbon feed of 93% wasstill being maintained after 40 hours.

Example 9 The general procedure of Example 7 was repeated except thatthe catalyst composition weighed 44.7 g. and consisted of 2.5% by weightof cobalt and 14;% by weight of molybdenum supported on gamma-alumina.

After a period of 29 hours a conversion eflioiency to CS based on thehydrocarbon feed of 82% was still being maintained.

6 Example 10 The hydrocarbon feed in this example was a petroleurdistillate of average formula C H which COIlSlSl of /v of saturatedaliphatic hydrocarbons, 14; /v of naphthenes and 6% /v of aromatichydroca: bons, and less than 4% of olefinic hydrocai bons, whichdistillate has a specific gravity at 15.5 15.5 C. of 0.706, 99% of thematerial distilling in the rang of 34 C. to 171 C. The general procedureof Exair ple 1 was repeated except that the nitrogen flow rate we 0.1l./hr. at R.T.P. and the catalyst zone was maintaine at a temperature of700 C. A conversion eflicienc based on hydrocarbons of 83.3% wasrealised over a pe rind of 40 hours.

What we claim is:

l. A process for the manufacture of carbon disulphid and by-producthydrogen sulphide which comprises reac' ing a preheated vaporisedhydrocarbon feed which 1 liquid at normal atmospheric temperature, whichis sul stantially completely vaporised at a temperature belo 200 C. andwhich consists mainly of hydrocarbons haw ing at least 5 carbon atoms inthe molecule with th stoichiometric amount of sulphur vapour required tocor vert the carbon content of said hydrocarbon to carbo disulfide andthe hydrogen content to hydrogen sulfid in the presence of a catalystfor conversion of hydrocai bon and sulfur to carbon disulfide byseparately intrr ducing the sulphur and the hydrocarbon feed into thcatalyst, the catalyst zone being maintained at a ten perature in therange 700 C. to 1300 C.

2. A process as claimed in claim 1 in which the reac tion zone ismaintained at a temperature in the approx mate range 800 C. to 900 C.

3. A process as claimed in claim 1 in which the cata lyst is potassiumvanadate supported on a member of th group consisting of silica gel andcorundum.

4. A process as claimed in claim 1 in which the rear tion is carried outin the presence of hydrogen.

5. A process as claimed in claim 1 in which the hydrc carbon feed is oneconsisting mainly of hydrocarbon having at least 6 carbon atoms in themolecule,

6. A process as claimed in claim 1 in which the hydrc carbon feed is onecontaining a predominating amour of saturated aliphatic hydrocarbons.

7. A process as described in claim 6 in which the hy drocarbon feed is alow grade petroleum distillate.

8. A process as set forth in claim 4 in which the hydrc gen is premixedwith the hydrocarbon feed before th feed is mixed with sulfur vapor.

References Cited in the file of this patent UNITED STATES PATENTS2,187,393 Simo Jan. 16, 194

1. A PROCESS FOR THE MANUFACTURE OF CARBON DISULPHIDE AND BY-PRODUCTHYDROGEN SULPHIDE WHICH COMPRISES REACTING A PRESHEATED VAPORISEDHYDROCARBON FEED WHICH IS LUQUID AT NORMAL ATMOSPHERIC TEMPERATURE,WHICH IS SUBSTANTIALLY COMPLETELY VAPORISED AT A TEMPERATURE BELOW200*C. AND WHICH CONSISTS MAINLY OF HYDROCARBONS HAVING AT LEAST 5CARBON ATOMS IN THE MOLECULE WITH THE STOICHIOMETRIC AMOUNT OF SULPHURVAPOR REQUIRED TO CONVERT THE CARBON CONTENT OF SAID HYDROCARBON TOCARBON DISULFIDE AND THE HYDROGEN CONTENT TO HYDROGEN SULFIDE IN THEPRESENCE OF A CATALYST FOR CONVERSION OF HYDROCARBON AND SULFUR TOCARBON DISULFIDE BY SEPARATELY INTRODUCTING THE SULPHUR AND THEHYDROCARBON FEED INTO THE CATALYST, THE CATALYST ZONE BEING MAINTAINEDAT A TEMPERATURE IN THE RANGE 700*C. TO 1300*C.